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// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef LIB_ZIRCON_ASSERT_ZIRCON_ASSERT_H_
#define LIB_ZIRCON_ASSERT_ZIRCON_ASSERT_H_
// For a description of which asserts are enabled at which debug levels, see the documentation for
// GN build argument |assert_level|.
#ifdef _KERNEL
#include <assert.h>
#define ZX_PANIC(args...) PANIC(args)
#define ZX_ASSERT(args...) ASSERT(args)
#define ZX_ASSERT_MSG(args...) ASSERT_MSG(args)
#define ZX_DEBUG_ASSERT(args...) DEBUG_ASSERT(args)
#define ZX_DEBUG_ASSERT_MSG(args...) DEBUG_ASSERT_MSG(args)
#define ZX_DEBUG_ASSERT_COND(args...) DEBUG_ASSERT_COND(args)
#define ZX_DEBUG_ASSERT_MSG_COND(args...) DEBUG_ASSERT_MSG_COND(args)
#define ZX_DEBUG_ASSERT_IMPLEMENTED DEBUG_ASSERT_IMPLEMENTED
#else // #ifdef _KERNEL
#include <zircon/compiler.h>
__BEGIN_CDECLS
// NOLINTNEXTLINE(bugprone-reserved-identifier)
void __zx_panic(const char* format, ...) __NO_RETURN __PRINTFLIKE(1, 2);
__END_CDECLS
#define ZX_PANIC(fmt, ...) __zx_panic((fmt), ##__VA_ARGS__)
// Conditionally implement ZX_DEBUG_ASSERT based on ZX_ASSERT_LEVEL.
//
// ZX_DEBUG_ASSERT_IMPLEMENTED is intended to be used to conditionalize code
// that is logically part of a debug assert. It's useful for performing complex
// consistency checks that are difficult to work into a ZX_DEBUG_ASSERT
// statement.
#ifdef ZX_ASSERT_LEVEL
#define ZX_DEBUG_ASSERT_IMPLEMENTED (ZX_ASSERT_LEVEL > 1)
#else
#define ZX_DEBUG_ASSERT_IMPLEMENTED 0
#endif
// Notes about the C++ and C versions of the assert macros.
//
// The C++ versions of these macros follow a very specific form for testing the
// assert predicate `x`. Specifically, the test of the predicate is _always_
// written simply as `if (x)`. Not:
//
// 1) `if (!x)` // or
// 2) `if ((x))` // or
// 3) `if (unlikely(!(x))) // or
// 4) `if (ZX_DEBUG_ASSERT_ENABLED && unlikely(!(x))) // or, anything else.
//
// It is *always* just `if (x)`. There is a method to this madness. The
// primary reason for this is to catch mistakes of the following form:
//
// ZX_DEBUG_ASSERT(my_bool_variable = false);
// ZX_ASSERT(my_int_variable = 5);
//
// Both of these are examples of a pattern where a code author meant to use
// comparison (`==`), but accidentally used assignment (`=`), meaning that the
// first of these examples is always going to fire, while the second will never
// fire. Both of them will have a side effect of mutating their variable, but a
// ZX_DEBUG_ASSERT's mutation will drop out of a release build.
//
// :: Accidental Assignment Protection ::
//
// This is all very bad, and _should_ be caught by the -Wparentheses warning,
// when enabled (which it usually is). Unfortunately, surrounding an assignment
// operation in a set of `()` will suppress the warning. Pretty much any other
// form of the predicate test ends up requiring that we add in an extra pair of
// `()`. This also includes wrapping the predicate in things like `unlikely(x)`
// and `likely(x)`. So, we have to restrict ourselves strictly to testing with
// `if (x)` in order to get the accidental assignment protection we desire.
//
// :: Temporary Variable Latching ::
//
// A surprise advantage to taking this approach is that it allows us (in C++) to
// more easily write predicates which involve latching to a temporary variable.
// Consider a case where we want to debug assert something about a value
// returned by a function which is expensive to call. We could write:
//
// DEBUG_ASSERT_MSG(Expensive() == 5,
// "Expensive() returned a non-five value (%u)",
// Expensive());
//
// But now we are calling the expensive function twice. We could also say:
//
// [[maybe_unused]] const uint32_t e = Expensive();
// ZX_DEBUG_ASSERT_MSG(e, "Expensive() returned a non-five value (%u)", e);
//
// but it takes a couple of lines, we have to add in a [[maybe_unused]]
// annotation, and we may still be forced to evaluate Expensive if the compiler
// cannot tell that it is guaranteed to have no side effects.
//
// With the new only-`if (x)` form of testing the predicate, however, we can do
// better. Now, we can write:
//
// ZX_DEBUG_ASSERT_MSG(const uint32_t e = Expensive(); e == 5,
// "Expensive() returned a non-five value (%u)", e);
//
// We still get our protection against accidental assignment, we are guaranteed
// to evaluate Expensive exactly once in a debug build, and zero times in a
// release build.
//
// :: WARNING - C code does not get these benefits ::
//
// To write in this style, but also preserve the likely/unlikely hinting
// benefits, we are forced to use C++'s standardized attributes `[[likely]]` and
// `[[unlikely]]``. These are not available in C, which has to use the old
// compiler attribute macros, which always end up introducing `()`, and
// suppressing the accidental assignment protection. Right now, there is no
// good way around this, and as long as we are building C code using this
// header, we will need to maintain a version of these macros which do not offer
// the same level of protection.
//
#ifdef __cplusplus
// Only use the [[likely]] attribute if we are sure the compiler is going to
// understand it.
#if defined(__has_cpp_attribute) && (__has_cpp_attribute(likely) >= 201803L)
// NOLINTNEXTLINE(bugprone-reserved-identifier)
#define _ZIRCON_ASSERT_ATTRIBUTE_LIKELY [[likely]]
#else
// NOLINTNEXTLINE(bugprone-reserved-identifier)
#define _ZIRCON_ASSERT_ATTRIBUTE_LIKELY
#endif
// Assert that |x| is true, else panic.
//
// ZX_ASSERT is always enabled and |x| will be evaluated regardless of any build arguments.
#define ZX_ASSERT(x) \
do { \
if (x) \
_ZIRCON_ASSERT_ATTRIBUTE_LIKELY { break; } \
else { /* NOLINT(readability-else-after-return) */ \
ZX_PANIC("ASSERT FAILED at (%s:%d): %s", __FILE__, __LINE__, #x); \
} \
} while (0)
// Assert that |x| is true, else panic with the given message.
//
// ZX_ASSERT_MSG is always enabled and |x| will be evaluated regardless of any build arguments.
#define ZX_ASSERT_MSG(x, msg, msgargs...) \
do { \
if (x) \
_ZIRCON_ASSERT_ATTRIBUTE_LIKELY { break; } \
else { \
ZX_PANIC("ASSERT FAILED at (%s:%d): %s" msg, __FILE__, __LINE__, #x, ##msgargs); \
} \
} while (0)
// Assert that |x| is true, else panic.
//
// Depending on build arguments, ZX_DEBUG_ASSERT may or may not be enabled. When disabled, |x| will
// not be evaluated.
#define ZX_DEBUG_ASSERT(x) \
do { \
if (ZX_DEBUG_ASSERT_IMPLEMENTED) { \
if (x) \
_ZIRCON_ASSERT_ATTRIBUTE_LIKELY { break; } \
else { \
ZX_PANIC("DEBUG ASSERT FAILED at (%s:%d): %s", __FILE__, __LINE__, #x); \
} \
} \
} while (0)
// Assert that |x| is true, else panic with the given message.
//
// Depending on build arguments, ZX_DEBUG_ASSERT_MSG may or may not be enabled. When disabled, |x|
// will not be evaluated.
#define ZX_DEBUG_ASSERT_MSG(x, msg, msgargs...) \
do { \
if (ZX_DEBUG_ASSERT_IMPLEMENTED) { \
if (x) \
_ZIRCON_ASSERT_ATTRIBUTE_LIKELY { break; } \
else { \
ZX_PANIC("DEBUG ASSERT FAILED at (%s:%d): %s" msg, __FILE__, __LINE__, #x, ##msgargs); \
} \
} \
} while (0)
#else // #ifdef __cplusplus
// Assert that |x| is true, else panic.
//
// ZX_ASSERT is always enabled and |x| will be evaluated regardless of any build arguments.
#define ZX_ASSERT(x) \
do { \
if (unlikely(!(x))) { \
ZX_PANIC("ASSERT FAILED at (%s:%d): %s", __FILE__, __LINE__, #x); \
} \
} while (0)
// Assert that |x| is true, else panic with the given message.
//
// ZX_ASSERT_MSG is always enabled and |x| will be evaluated regardless of any build arguments.
#define ZX_ASSERT_MSG(x, msg, msgargs...) \
do { \
if (unlikely(!(x))) { \
ZX_PANIC("ASSERT FAILED at (%s:%d): %s" msg, __FILE__, __LINE__, #x, ##msgargs); \
} \
} while (0)
// Assert that |x| is true, else panic.
//
// Depending on build arguments, ZX_DEBUG_ASSERT may or may not be enabled. When disabled, |x| will
// not be evaluated.
#define ZX_DEBUG_ASSERT(x) \
do { \
if (ZX_DEBUG_ASSERT_IMPLEMENTED && unlikely(!(x))) { \
ZX_PANIC("DEBUG ASSERT FAILED at (%s:%d): %s", __FILE__, __LINE__, #x); \
} \
} while (0)
// Assert that |x| is true, else panic with the given message.
//
// Depending on build arguments, ZX_DEBUG_ASSERT_MSG may or may not be enabled. When disabled, |x|
// will not be evaluated.
#define ZX_DEBUG_ASSERT_MSG(x, msg, msgargs...) \
do { \
if (ZX_DEBUG_ASSERT_IMPLEMENTED && unlikely(!(x))) { \
ZX_PANIC("DEBUG ASSERT FAILED at (%s:%d): %s" msg, __FILE__, __LINE__, #x, ##msgargs); \
} \
} while (0)
#endif // #ifdef __cplusplus
//
// implement _COND versions of ZX_DEBUG_ASSERT which only emit the body if
// ZX_DEBUG_ASSERT_IMPLEMENTED is set
#if ZX_DEBUG_ASSERT_IMPLEMENTED
#define ZX_DEBUG_ASSERT_COND(x) ZX_DEBUG_ASSERT(x)
#define ZX_DEBUG_ASSERT_MSG_COND(x, msg, msgargs...) ZX_DEBUG_ASSERT_MSG(x, msg, msgargs)
#else
#define ZX_DEBUG_ASSERT_COND(x) \
do { \
} while (0)
#define ZX_DEBUG_ASSERT_MSG_COND(x, msg, msgargs...) \
do { \
} while (0)
#endif
#endif // #ifdef _KERNEL
#endif // LIB_ZIRCON_ASSERT_ZIRCON_ASSERT_H_
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